I. Field of the Invention
The present invention relates generally to microwave lenses and, more particularly, to a microwave lens constructed of a metamaterial with a MEMS device to vary the resonant frequency of the lens.
II. Description of Related Art
The use of metamaterials in microwave applications, such as automotive radar systems, continues to expand. Such metamaterials exhibit properties in response to incident electromagnetic radiation which vary as a function of the shape of the metamaterial rather than the composition of the metamaterial.
Conventionally, the metamaterial comprises a plurality of inductive-capacitive (LC) cells that are arranged in an array. Often, the array is planar and a plurality of arrays are stacked one upon each other to form the microwave lens. Each cell, furthermore, is relatively small relative to the wavelength of the incident radiation, typically in the range of 1/10λ.
Each cell in the array forms an LC resonator which resonates in response to incident electromagnetic radiation at frequencies which vary as a function of the shape of the LC cell. As such, the microwave lens may be utilized to focus, defocus, steer or otherwise control a beam of microwave electromagnetic radiation directed through the lens.
One disadvantage of the previously known microwave lenses using metamaterials, however, is that the resonant frequency of the metamaterial, and thus of the lens, is fixed. In many situations, however, it would be useful to vary the resonant frequency of the lens.
One way to modify the resonant frequency of the lens is to provide a voltage controlled variable capacitor for each resonator cell which would effectively modify the resonant frequency of the cell, and thus the resonant frequency of the overall microwave lens as the value of the capacitor changes. The provision of voltage biasing lines for such variable capacitors, however, has proven problematic due in large part to the small size of each resonator cell. The provision of separate voltage biasing lines between the variable capacitors in such resonator cells also increases the number of manufacturing steps necessary to manufacture the microwave lens, and thus the overall cost of the lens.